Floods that have devastated north-central Colorado, killing
eight people and displacing thousands, have also dislodged
storage tanks that hold drilling wastewater left over from the
production process known as hydraulic fracturing, or fracking.

While the impact of leaks is yet to be assessed,
environmental groups, which oppose fracking, are expressing
concerns about the risk of adding drilling fluids to other
toxins potentially loosed by the floods.

Fertilizer and pesticides running from vast tracts of
farmland may pose a bigger threat. But fracking waste is one of
the newest problems in a state where energy production is on the
rise, and spills could pose the latest environmental challenge
to the multibillion-dollar oil and gas industry.

"We don't know the disposition of the chemicals and waste at
this point, but there's a possibility that the flooding allowed
their release, and that is a major concern," said Tony
Ingraffea, professor of engineering at Cornell University in
Ithaca, New York.

"We could have a long term, hazardous waste cleanup
problem."

A helicopter flight on Tuesday over Weld County in Colorado,
one of the worst affected areas and home to about 20,000 active
oil and gas wells, afforded views of listing and toppled storage
tanks at oil and gas wells. Some sites were submerged under
brown floodwater; cattle grazed on higher ground nearby.

Encana Corp, a major driller in the state, said
flooding had dislodged some storage tanks holding wastewater at
oil and gas wells, and a "small amount" of oil had spilled from
one well. The spill was contained at the site, a spokesman said.
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